all mpu60x0 init: removed fifo configuration, disabled fifo, use PLL_Z_CLK
Rationale for PLL_Z_CLK is a comment in PX4 mpu6000 driver which says that z has better performance:
https://github.com/PX4/Firmware/blob/master/apps/drivers/mpu6000/mpu6000.cpp#L373
pios_mpu60x0: remove fifo settings from device configuration structure
pios_mpu60x0: synced drivers, simplified init sequence
pios_mpu6000: fixed FreeRTOS api misusage within interrupt context